Such devices are usually designed for dispensing measured amounts of a liquid product, and for watertight sealing of the neck of a bottle containing said liquid product to be dispensed.
Devices of this type exist forming a pump and comprising a pump body, a piston mounted fixed in the pump body, a dosage chamber with variable volume into which the end of the piston opens, the chamber communicating with the outside by means of a release valve enclosed in a push button, allowing a dose of product to be dispensed when it is pressed. In addition, the end of the piston is closed by a valve or a second valve for intaking the liquid product in the chamber.
Such devices have certain disadvantages, in particular in the pharmaceutical field, since the doses of product dispensed can vary from one spray to the next, while the dispensing of accurate doses is required.
Furthermore, when such devices are implemented on bottles without air intake, for example with deformable walls, the pump must have sufficient suction power to reduce the volume of the container. This demand is difficult to meet, which can affect the precision of the doses of product dispensed.
Moreover, such devices are very sensitive and their reliability is not always guaranteed. The manufacturer must ensure that the elements forming the pump are centred and aligned around the axis of symmetry of said pump, at the risk of malfunctions that can result in incomplete doses and/or reduced suction power. In addition, when activating the pump, the user must make sure to press the centre of the push button, in order not to cause the compression elements to move off centre and to avoid breaking the seal between the valve and the dosage chamber.
Furthermore, the known devices entail problems when priming the pump. Indeed, due to their design, it is difficult to vent the air contained in the dosage chamber before using the dispenser for the first time.